Focusing structure in an information reading apparatus

Abstract

In an automatic sorting system for sorting objects conveyed on a conveyor, a camera is used for pattern recognition of the object being sorted. Due to the difference in sizes of the objects being sorted, the camera must be focused depending on the size of the object under consideration. Instead of moving the camera section itself, an optical path bending section can be included between the camera and the objects to be examined. The optical path bending section includes at least one pair of reflector mirrors disposed so that the reflecting surfaces thereof face each other at an angle of 90 degrees. In order to enable focusing for different sized objects, the optical path bending section can be moved in a direction parallel to the optical paths entering and exiting the optical path bending section.

What is claimed is: 
     
       1. An information reading system which reads an upper, information indicating surface of each of a plurality of objects having differing heights and being moved on a conveyor, said information reading system comprising: a fixed camera section for reading said information indicating surface using rays of light, said information indicating surface being read while said object is being conveyed;   mirror means disposed between said fixed camera section and said information indicating surface including at least one pair of reflector mirrors having reflecting surfaces which face each other at an angle of 90 degrees so that said rays of light are reflected from said fixed camera section, through said mirror means, and to said information indicating surface;   focusing means for focusing said fixed camera section on said information indicating surface by moving said mirror means to equalize an optical path from said fixed camera section to said information reading surface of each of said objects such that an optical path from said information indicating surface of an object to said fixed camera section is substantially unchanged during reading of said information indicating surface of said object; and   means for illuminating said information indicating surface of each of said objects with illuminating light, said illuminating means being positioned in the optical path from said information indicating surface to said fixed camera section,   wherein an optical path of said illuminating light coincides with that of said rays of light used for reading said information indicating surface of each of said objects.   
     
     
       2. The information reading system claimed in claim 1, wherein said mirror means includes only one pair of reflector mirrors. 
     
     
       3. The information reading system claimed in claim 2, wherein said focusing means moves said mirror means a distance equal to one-half of the difference in height between a previous object and a present object being examined in order to focus said camera section on said information indicating surface of said present object. 
     
     
       4. The information reading system claimed in claim 1, wherein said mirror means includes two pair of reflector mirrors. 
     
     
       5. The information reading system claimed in claim 4, wherein said focusing means moves said mirror means a distance equal to one-quarter of the difference in height between a previous object and a present object being examined in order to focus the camera section on said information indicating surface of said present object. 
     
     
       6. The information reading system claimed in claim 1, wherein said focusing means moves said mirror means in a direction parallel to the direction of the light rays entering and exiting the mirror means. 
     
     
       7. The information reading system claimed in claim 1, wherein said mirror means includes N pair of reflector mirrors (N being an integer greater than or equal to one) and said focusing means moves said mirror means a distance L satisfying the equation: ##EQU1## wherein H is the difference in height between a previous object and a present object being examined in order to focus said camera section on said information indicating surface of said present object. 
     
     
       8. An information reading system for reading information from upper surfaces of objects having differing heights and being conveyed, said system reading said information from said surfaces with rays of light, said system comprising: a camera having an optical path extending between said camera and each of said upper surfaces;   focussing means for focussing said camera on said upper surfaces, said surfaces being read while said objects are being conveyed and said focusing means comprising mirror means disposed in said optical path and receiving entrance light in a first direction while providing exit light in a second direction opposite and parallel to said first direction, said mirror means being movable in said first and second directions to vary the effective length of said optical path without moving said camera to equalize said optical path from said camera to an upper surface of each of said objects such that said optical path from said camera to said upper surface of each of said objects being focussed upon is substantially unchanged during focussing on said surface; and   means for illuminating said upper surface of each of said objects with illuminating light, said illuminating mans being positioned in the optical path from said upper surface to said camera,   wherein an optical path of said illuminating light coincides with that of said rays of light used for reading said upper surface of each of said objects.   
     
     
       9. The information reading system claimed in claim 8, wherein said mirror means reverses the direction of said optical path N times, where N is an integer, and said mirror means is moved a distance of L/2N to change the length of said optical path by a distance L. 
     
     
       10. The information reading system claimed in claim 8, wherein said mirror means includes two mirrors angled by 90° with respect to one another. 
     
     
       11. The information reading system claimed in claim 10, wherein said objects are movable along a conveyor and wherein said two mirrors are movable substantially parallel to a direction of movement of said objects on said conveyor.